/**
 * 贝塞尔平滑曲线 
 * @module zrender/shape/util/smoothBezier
 * @author pissang (https://www.github.com/pissang) 
 *         Kener (@Kener-林峰, kener.linfeng@gmail.com)
 *         errorrik (errorrik@gmail.com)
 */


var vector = require('../../tool/vector');
module.exports = function (points, smooth, isLoop, constraint) {
    var cps = [];
    var v = [];
    var v1 = [];
    var v2 = [];
    var prevPoint;
    var nextPoint;
    var hasConstraint = !!constraint;
    var min, max;
    if (hasConstraint) {
        min = [
            Infinity,
            Infinity
        ];
        max = [
            -Infinity,
            -Infinity
        ];
        for (var i = 0, len = points.length; i < len; i++) {
            vector.min(min, min, points[i]);
            vector.max(max, max, points[i]);
        }
        // 与指定的包围盒做并集
        vector.min(min, min, constraint[0]);
        vector.max(max, max, constraint[1]);
    }
    for (var i = 0, len = points.length; i < len; i++) {
        var point = points[i];
        var prevPoint;
        var nextPoint;
        if (isLoop) {
            prevPoint = points[i ? i - 1 : len - 1];
            nextPoint = points[(i + 1) % len];
        } else {
            if (i === 0 || i === len - 1) {
                cps.push(vector.clone(points[i]));
                continue;
            } else {
                prevPoint = points[i - 1];
                nextPoint = points[i + 1];
            }
        }
        vector.sub(v, nextPoint, prevPoint);
        // use degree to scale the handle length
        vector.scale(v, v, smooth);
        var d0 = vector.distance(point, prevPoint);
        var d1 = vector.distance(point, nextPoint);
        var sum = d0 + d1;
        if (sum !== 0) {
            d0 /= sum;
            d1 /= sum;
        }
        vector.scale(v1, v, -d0);
        vector.scale(v2, v, d1);
        var cp0 = vector.add([], point, v1);
        var cp1 = vector.add([], point, v2);
        if (hasConstraint) {
            vector.max(cp0, cp0, min);
            vector.min(cp0, cp0, max);
            vector.max(cp1, cp1, min);
            vector.min(cp1, cp1, max);
        }
        cps.push(cp0);
        cps.push(cp1);
    }
    if (isLoop) {
        cps.push(vector.clone(cps.shift()));
    }
    return cps;
} || module.exports;;